Method, system and apparatus for navigational assistance

ABSTRACT

An assistive navigational system for deployment in a facility having a global frame of reference includes: a server including a memory storing: a plurality of anchor definitions each containing (i) an anchor position in the global frame of reference, and (ii) a feature set corresponding to physical characteristics of the facility at the anchor position; and a task definition containing (i) a task position defined relative to the anchor position, and (ii) task overlay data; the server further including a communications interface, and a processor configured to: select one of the anchor definitions for association with the task definition; and transmit the selected anchor definition and the task definition to a mobile computing device, the mobile computing device configured to receive the selected anchor definition and the task definition; the mobile computing device further configured to present the task overlay data on a display.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/217,296, filed Dec. 12, 2018, entitled “Method, System and Apparatusfor Navigational Assistance,” which is incorporated herein by referencein its entirety.

BACKGROUND

Environments in which objects are managed, such as retail facilities,may be complex and fluid. For example, a retail facility may includeobjects such as products for purchase, a distribution environment mayinclude objects such as parcels or pallets, a manufacturing environmentmay include objects such as components or assemblies, a healthcareenvironment may include objects such as medications or medical devices.

Tasks may be identified for execution within such environments, forexample to correct price labels on products, restock a supply ofproducts, and the like. Such tasks may be assigned to human operatorsfor execution. The presence of a variable number of tasks, as well as avariable number of mobile operators, within the environment at any giventime can lead to inefficient allocation of tasks to operators, resultingin underutilization or overutilization of certain operators or the needfor expensive training of multiple operators on multiple tasks.

Further, the operator assigned to perform a given task may be requiredto accurately locate a position within the facility at which the task isto be performed. A mobile computing device carried by the operator mayhave insufficiently accurate localization to guide the operator to thecorrect position within the facility, resulting in incorrectly executedtasks, delays in task execution, or both.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that include the claimed invention, and explainvarious principles and advantages of those embodiments.

FIG. 1 is a schematic of a mobile automation system.

FIG. 2A depicts a mobile automation apparatus in the system of FIG. 1 .

FIG. 2B is a block diagram of certain internal hardware components ofthe mobile automation apparatus in the system of FIG. 1 .

FIG. 3 is a flowchart of a method of generating and deployingnavigational assistance information in the system of FIG. 1 .

FIG. 4A is an overhead view of a facility illustrating an anchorposition.

FIG. 4B depicts an anchor feature set employed in the method of FIG. 3 .

FIG. 5A depicts task overlay data employed in the method of FIG. 3 .

FIG. 5B depicts a further overhead view of the facility of FIG. 4A,illustrating anchor and device positions.

FIG. 6 depicts an anchor guide prompt generated at block 355 of themethod of FIG. 3 .

FIG. 7A depicts an overhead view of the facility of FIG. 4 during theperformance of the method of FIG. 3 .

FIG. 7B depicts image data captured by the client device.

FIG. 8A depicts a further overhead view of the facility of FIG. 4 duringthe performance of the method of FIG. 3 .

FIG. 8B depicts image data captured by the client device.

FIG. 9A depicts a further overhead view of the facility of FIG. 4 duringthe performance of the method of FIG. 3 .

FIG. 9B depicts the presentation of task overlay information responsiveto arrival of the client device at the position shown in FIG. 9A.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

The apparatus and method components have been represented whereappropriate by conventional symbols in the drawings, showing only thosespecific details that are pertinent to understanding the embodiments ofthe present invention so as not to obscure the disclosure with detailsthat will be readily apparent to those of ordinary skill in the arthaving the benefit of the description herein.

DETAILED DESCRIPTION

Examples disclosed herein are directed to a method of navigationalassistance at a mobile computing device for deployment in a facilityhaving a global frame of reference, the method comprising: receiving ananchor definition containing (i) an anchor position in the global frameof reference, and (ii) a feature set corresponding to physicalcharacteristics of the facility at the anchor position; receiving a taskdefinition containing (i) a task position defined relative to the anchorposition, and (ii) task overlay data; capturing, using an image capturemodule, a sequence of images; responsive to detecting the feature set inthe sequence of images, determining a local device position of themobile computing device relative to the anchor position; based on thelocal device position and the task position, determining whether thetask position is within a field of view of the mobile computing device;and responsive to determining that the task position is within the fieldof view, presenting the sequence of images overlaid with the overlaydata on a display.

Additional examples disclosed herein are directed to a mobile computingdevice for navigational assistance in a facility having a global frameof reference, the mobile computing device comprising: a memory storing:an anchor definition containing (i) an anchor position in the globalframe of reference, and (ii) a feature set corresponding to physicalcharacteristics of the facility at the anchor position; and a taskdefinition containing (i) a task position defined relative to the anchorposition, and (ii) task overlay data; a display; an image capture moduleconfigured to capture a sequence of images; a processor connected to thememory, the display and the image capture module, the processorconfigured to: responsive to detecting the feature set in the sequenceof images, determine a local device position of the mobile computingdevice relative to the anchor position; based on the local deviceposition and the task position, determine whether the task position iswithin a field of view of the mobile computing device; and responsive todetermining that the task position is within the field of view, controlthe display to present the sequence of images overlaid with the overlaydata on a display.

Further examples disclosed herein are directed to an assistivenavigational system for deployment in a facility having a global frameof reference, the system comprising: a server including a memorystoring: a plurality of anchor definitions each containing (i) an anchorposition in the global frame of reference, and (ii) a feature setcorresponding to physical characteristics of the facility at the anchorposition; and a task definition containing (i) a task position definedrelative to the anchor position, and (ii) task overlay data; the serverfurther including a communications interface, and a processor configuredto: select one of the anchor definitions for association with the taskdefinition; and transmit the selected anchor definition and the taskdefinition to a mobile computing device, the mobile computing deviceconfigured to receive the selected anchor definition and the taskdefinition; the mobile computing device further configured to presentthe task overlay data on a display.

FIG. 1 depicts a mobile automation and navigational system 100 inaccordance with the teachings of this disclosure. The system 100 isillustrated as being deployed in a retail environment, but in otherembodiments can be deployed in a variety of other environments,including warehouses, manufacturing facilities, hospitals, and the like.The above-noted environments are referred to herein generically asfacilities. The system 100 includes a server 101 in communication withat least one mobile automation apparatus 103 (also referred to hereinsimply as the apparatus 103) and at least one client computing device105 (also referred to herein as a mobile computing device 105) viacommunication links 107, illustrated in the present example as includingwireless links. In the present example, the links 107 are provided by awireless local area network (WLAN) deployed within the retailenvironment by one or more access points (not shown). In other examples,the server 101, the client device 105, or both, are located outside theretail environment, and the links 107 therefore include wide-areanetworks such as the Internet, mobile networks, and the like. The system100 also includes a dock 108 for the apparatus 103 in the presentexample. The dock 108 is in communication with the server 101 via a link109 that in the present example is a wired link. In other examples,however, the link 109 is a wireless link.

The client computing device 105 is illustrated in FIG. 1 as a mobilecomputing device, such as a tablet, smart phone or the like. In otherexamples, the client device 105 is implemented as another type of mobilecomputing device, such as a laptop computer, a desktop computer mountedon a mobile cart, a dedicated vehicle computer (as in a forklift), smartglasses, a virtual-reality headset, or the like. The system 100 caninclude a plurality of client devices 105 in communication with theserver 101 via respective links 107.

The system 100 is deployed, in the illustrated example, in a retailfacility including a plurality of shelf modules 110-1, 110-2, 110-3 andso on (collectively referred to as shelves 110, and generically referredto as a shelf 110—this nomenclature is also employed for other elementsdiscussed herein). Each shelf module 110 supports a plurality ofproducts 112. Each shelf module 110 includes a shelf back 116-1, 116-2,116-3 and a support surface (e.g. support surface 117-3 as illustratedin FIG. 1 ) extending from the shelf back 116 to a shelf edge 118-1,118-2, 118-3.

The shelf modules 110 are typically arranged in a plurality of aisles,each of which includes a plurality of modules 110 aligned end-to-end. Insuch arrangements, the shelf edges 118 face into the aisles, throughwhich customers in the retail environment as well as the apparatus 103may travel. As will be apparent from FIG. 1 , the term “shelf edge” 118as employed herein, which may also be referred to as the edge of asupport surface (e.g., the support surfaces 117) refers to a surfacebounded by adjacent surfaces having different angles of inclination. Inthe example illustrated in FIG. 1 , the shelf edge 118-3 is at an angleof about ninety degrees relative to each of the support surface 117-3and the underside (not shown) of the support surface 117-3. In otherexamples, the angles between the shelf edge 118-3 and the adjacentsurfaces, such as the support surface 117-3, is more or less than ninetydegrees.

The apparatus 103 is deployed within the retail facility, andcommunicates with the server 101 (e.g. via the link 107) to navigate,autonomously or partially autonomously, along a length 119 of at least aportion of the shelves 110. The apparatus 103 is equipped with aplurality of navigation and data capture sensors 104, such as imagesensors (e.g. one or more digital cameras) and depth sensors (e.g. oneor more Light Detection and Ranging (LIDAR) sensors, one or more depthcameras employing structured light patterns, such as infrared light, orthe like). The apparatus 103 can be configured to employ the sensors 104to both navigate among the shelves 110 (e.g. according to the pathsmentioned above) and to capture shelf data during such navigation.

The server 101 includes a special purpose controller, such as aprocessor 120, specifically designed to control and/or assist the mobileautomation apparatus 103 to navigate the environment and to capturedata. The processor 120 can be further configured to obtain the captureddata via a communications interface 124 for storage in a repository 132and subsequent processing, e.g. to detect objects such as shelvedproducts in the captured data, and detect status informationcorresponding to the objects.

The server 101 may also be configured to transmit status notifications(e.g. notifications indicating that products are out-of-stock, low stockor misplaced) to the client device 105 responsive to the determinationof product status data. The status notifications, as will be discussedin greater detail below, are provided to the client device 105 in theform of task definitions, indicating what tasks are to be performed(e.g. by a human operator of the client device 105) to correct thestatus of one or more objects. The server 101 is further configured toprovide to the client device 105, along with the above-noted taskdefinitions, navigational information that the client device 105 isconfigured to process to guide the operator to the appropriate locationwithin the facility for execution of the task (e.g. to correct a pricelabel, relocate is misplaced product, and the like). Navigationalinformation can include positions within the facility defined accordingto a global frame of reference 102 (e.g. a coordinate system).

The processor 120 is interconnected with a non-transitory computerreadable storage medium, such as the above-mentioned memory 122, havingstored thereon computer readable instructions for performing variousfunctionality, including control of the apparatus 103 to capture shelfdata, post-processing of the shelf data, and generating and providingtask and navigational data to the client device 105. The memory 122includes a combination of volatile (e.g. Random Access Memory or RAM)and non-volatile memory (e.g. read only memory or ROM, ElectricallyErasable Programmable Read Only Memory or EEPROM, flash memory). Theprocessor 120 and the memory 122 each comprise one or more integratedcircuits. In some embodiments, the processor 120 is implemented as oneor more central processing units (CPUs) and/or graphics processing units(GPUs).

The server 101 also includes the above-mentioned communicationsinterface 124 interconnected with the processor 120. The communicationsinterface 124 includes suitable hardware (e.g. transmitters, receivers,network interface controllers and the like) allowing the server 101 tocommunicate with other computing devices—particularly the apparatus 103,the client device 105 and the dock 108—via the links 107 and 109. Thelinks 107 and 109 may be direct links, or links that traverse one ormore networks, including both local and wide-area networks. The specificcomponents of the communications interface 124 are selected based on thetype of network or other links that the server 101 is required tocommunicate over. In the present example, as noted earlier, a wirelesslocal-area network is implemented within the retail environment via thedeployment of one or more wireless access points. The links 107therefore include either or both wireless links between the apparatus103 and the mobile device 105 and the above-mentioned access points, anda wired link (e.g. an Ethernet-based link) between the server 101 andthe access point.

The memory 122 stores a plurality of applications, each including aplurality of computer readable instructions executable by the processor120. The execution of the above-mentioned instructions by the processor120 configures the server 101 to perform various actions discussedherein. The applications stored in the memory 122 include a controlapplication 128, which may also be implemented as a suite of logicallydistinct applications. In general, via execution of the application 128or subcomponents thereof and in conjunction with the other components ofthe server 101, the processor 120 is configured to implement variousfunctionality related to generating or otherwise obtaining taskdefinitions and navigational information for provision to the clientdevice 105 to guide an operator of the client device 105 to theappropriate location within the facility to perform one or more tasks,as noted above. The processor 120, as configured via the execution ofthe control application 128, is also referred to herein as thecontroller 120. As will now be apparent, some or all of thefunctionality implemented by the controller 120 described below may alsobe performed by preconfigured special purpose hardware controllers (e.g.one or more FPGAs and/or Application-Specific Integrated Circuits(ASICs) configured for navigational computations) rather than byexecution of the control application 128 by the processor 120.

The client device 105 includes a special-purpose controller, such as aprocessor 150, interconnected with a non-transitory computer readablestorage medium, such as a memory 152. The memory 152 includes acombination of volatile (e.g. Random Access Memory or RAM) andnon-volatile memory (e.g. read only memory or ROM, Electrically ErasableProgrammable Read Only Memory or EEPROM, flash memory). The processor150 and the memory 152 each comprise one or more integrated circuits.

The client device 105 also includes at least one input device 156interconnected with the processor 150. The input device 156 isconfigured to receive input and provide data representative of thereceived input to the processor 150. The input device 156 includes anyone of, or a suitable combination of, a touch screen, a keypad, atrigger button, a microphone, and the like. In addition, the clientdevice 105 includes a camera 158 including a suitable image sensor orcombination of image sensors. The camera 158 is configured to captureimages (e.g. single frames or video streams including sequences of imageframes) for provision to the processor 150.

The client device 105 also includes a display 160 (e.g. a flat-paneldisplay integrated with the above-mentioned touch screen) interconnectedwith the processor 150, and configured to render data under the controlof the processor 150. The client device 105 can also include one or moreoutput devices in addition to the display 160, such as a speaker, anotification LED, and the like (not shown).

The client device 105 also includes a communications interface 162interconnected with the processor 150. The communications interface 162includes any suitable hardware (e.g. transmitters, receivers, networkinterface controllers and the like) allowing the client device 105 tocommunicate with other computing devices via wired and/or wireless links(e.g. over local or wide-area networks). The specific components of thecommunications interface 162 are selected based on the type(s) ofnetwork(s) or other links that the client device 105 is required tocommunicate over.

Further, the client device 105 includes a motion sensor 164, such as aninertial measurement unit (IMU) including one or more accelerometers,one or more gyroscopes, and/or one or more magnetometers. The motionsensor 164 is configured to generate data indicating detected movementof the client device 105 and provide the data to the processor 150, forexample to enable the processor 150 to maintain one or morelocalizations of the client device 105 (i.e. with respect to the frameof reference 102 or a local frame of reference, as will be discussed ingreater detail below).

The memory 152 stores computer readable instructions for execution bythe processor 150. In particular, the memory 152 stores a navigationalassistance application 154 (also referred to simply as the application154) which, when executed by the processor 150, configures the processor150 to perform various functions discussed below in greater detail andrelated to the receipt and presentation of task and navigationalinformation. The application 150 may also be implemented as a suite ofdistinct applications in other examples.

The processor 150, when so configured by the execution of theapplication 154, may also be referred to as a navigational assistancecontroller 150. Those skilled in the art will appreciate that thefunctionality implemented by the processor 150 via the execution of theapplication 154 may also be implemented by one or more speciallydesigned hardware and firmware components, such as FPGAs, ASICs and thelike in other embodiments.

Turning now to FIGS. 2A and 2B, the mobile automation apparatus 103 isshown in greater detail. The apparatus 103 includes a chassis 201containing a locomotive mechanism 203 (e.g. one or more electricalmotors driving wheels, tracks or the like). The apparatus 103 furtherincludes a sensor mast 205 supported on the chassis 201 and, in thepresent example, extending upwards (e.g., substantially vertically) fromthe chassis 201. The mast 205 supports the sensors 104 mentionedearlier. In particular, the sensors 104 include at least one imagingsensor 207, such as a digital camera, as well as at least one depthsensor 209, such as a 3D digital camera. The apparatus 103 also includesadditional depth sensors, such as LIDAR sensors 211. In other examples,the apparatus 103 includes additional sensors, such as one or more RFIDreaders, temperature sensors, and the like.

In the present example, the mast 205 supports seven digital cameras207-1 through 207-7, and two LIDAR sensors 211-1 and 211-2. The mast 205also supports a plurality of illumination assemblies 213, configured toilluminate the fields of view of the respective cameras 207. That is,the illumination assembly 213-1 illuminates the field of view of thecamera 207-1, and so on. The sensors 207 and 211 are oriented on themast 205 such that the fields of view of each sensor face a shelf 110along the length 119 of which the apparatus 103 is travelling. Theapparatus 103 is configured to track a location of the apparatus 103(e.g. a location of the center of the chassis 201) in the global frameof reference 102 previously established in the retail facility,permitting data captured by the mobile automation apparatus 103 to beregistered to the common frame of reference. The above-mentionedlocation of the apparatus 103 within the frame of reference 102, alsoreferred to as localization, is employed in the generation of paths forexecution by the apparatus 103.

The mobile automation apparatus 103 includes a special-purposenavigational controller, such as a processor 220, as shown in FIG. 2B,interconnected with a non-transitory computer readable storage medium,such as a memory 222. The memory 222 includes a combination of volatile(e.g. Random Access Memory or RAM) and non-volatile memory (e.g. readonly memory or ROM, Electrically Erasable Programmable Read Only Memoryor EEPROM, flash memory). The processor 220 and the memory 222 eachcomprise one or more integrated circuits. The memory 222 stores computerreadable instructions for execution by the processor 220. In particular,the memory 222 stores a navigation application 228 which, when executedby the processor 220, configures the processor 220 to perform variousfunctions discussed below in greater detail and related to thenavigation of the apparatus 103 (e.g. by controlling the locomotivemechanism 203). The application 228 may also be implemented as a suiteof distinct applications in other examples.

The processor 220, when so configured by the execution of theapplication 228, may also be referred to as a navigational controller220. Those skilled in the art will appreciate that the functionalityimplemented by the processor 220 via the execution of the application228 may also be implemented by one or more specially designed hardwareand firmware components, such as FPGAs, ASICs and the like in otherembodiments.

The memory 222 may also store a repository 232 containing, for example,one or more maps of the environment in which the apparatus 103 operates,for use during the execution of the application 228. The apparatus 103may communicate with the server 101, for example to receive instructionsto navigate to specified locations and initiate data capture operations,via a communications interface 224 over the link 107 shown in FIG. 1 .The communications interface 224 also enables the apparatus 103 tocommunicate with the server 101 via the dock 108 and the link 109.

The functionality of the applications 128 and 154 will now be describedin greater detail. In particular, the generation of task andnavigational information for deployment to the client device 105 fromthe server 101, as well as the processing of the above-mentionedinformation at the client device 105, will be described.

Turning to FIG. 3 , a method 300 of generating and deployingnavigational assistance information is shown. As illustrated in FIG. 3 ,certain blocks of the method 300 are performed by the server 101, whileother blocks of the method 300 are performed by the client device 105.In other embodiments, the server 101 can be configured to performcertain blocks shown in FIG. 3 as being performed by the client device105. In still other embodiments, the client device 105 can be configuredto perform certain blocks shown in FIG. 3 as being performed by theserver 101.

At block 305, the server 101 is configured to obtain one or more anchordefinitions, for storage in the memory 122 (e.g. in the repository 132).Anchor definitions can be obtained at the server 101 during the initialdeployment of the system 100 in the facility. In general, an anchordefinition includes data defining a position within the facility. Theposition, in the present discussion, corresponds to a location accordingto the global frame of reference 102, as well as an orientation (e.g.yaw, pitch and roll angles at the above-mentioned location). Each anchordefinition also includes a feature set corresponding to physicalcharacteristics of the facility at the above-mentioned position. Inother words, an anchor definition defines various characteristics of thefacility when observed from the anchor position. As will be discussedbelow, the use of an anchor definition therefore permits other computingdevices, including the client device 105, to detect at least a portionof the feature set contained in the anchor definition. The client device105 can thereby determine a current position of the client device 105both globally (i.e. according to the frame of reference 102) andlocally, with respect to the anchor position.

Anchor definitions may be obtained in a variety of ways at block 305. Insome examples, each anchor definition is generated by a mobile datacapture device, such as a client device 105 or the apparatus 103. Inparticular, the mobile data capture device is placed (manually or viaautonomous or semi-autonomous navigation) at a known position accordingto the frame of reference 102. The known position corresponds to theanchor position mentioned above. The mobile data capture device is thenconfigured to capture data from the anchor position. The nature of thedata captured is not particularly limited. In the present example, thedata captured includes image data depicting physical structures withinthe facility surrounding the anchor position. That is, the mobile datacapture device includes an image sensor configured to capture one ormore image frames from the selected anchor position. The data capturedfor use in generating an anchor definition can also include depth scandata, for example acquired via lidar or depth camera. In furtherexamples, the captured data can include proximity indicators such aswireless access point signatures (e.g. one or more received signalstrength indicators (RSSI) and round trip times (RTT) for each of aplurality of access points detected from the anchor position), and/orbeacon signatures (e.g. one or more identifiers of beacons detectablefrom the anchor position, such as Bluetooth low energy (BLE) beaconidentifiers, visual light communication (VLC) emitter identifiers, andthe like).

Following data capture as described above, a feature set is extractedfrom the captured data, for storage (along with the anchor position) asthe anchor definition. A wide variety of features may be extracted togenerate the feature set. In the case of captured image data, featurescan include any suitable combination of geometric constructs such aslines, planes and polygons, extracted via the execution of suitable edgeand plane detection operations (e.g. random sample consensus (RANSAC),Sobel filters, and the like). Features extracted from image data canalso include color and/or brightness histograms. Feature extraction maybe performed at the capture device mentioned above, or at the server 101upon receipt of the captured data from the capture device. Followingdata capture and feature extraction, the feature set is stored alongwith the global anchor position as an anchor definition in the memory122 (e.g. in the repository 132).

FIGS. 4A and 4B illustrate the generation of an example anchordefinition. In particular, FIG. 4A illustrates an overhead view of afacility 400 such as a retail facility containing a plurality of rows404-1, 404-2, 404-3, 404-4, 404-5, 404-6 and 404-7 of shelf modulesforming aisles. As seen in FIG. 4A, each row 404 occupies a region ofthe facility 400, which can be expressed as a set of coordinates in theglobal frame of reference 102. An anchor position 408 is also shown inFIG. 4A, defined by a location (e.g. the center of the circular elementof the anchor position 408) and an orientation (e.g. the directionindicated by the arrow of the anchor position 408).

FIG. 4B illustrates image data 412 captured by a mobile data capturedevice (e.g. the apparatus 103 or the client device 105) during thecreation of the anchor definition. In particular, the image data 412includes an image frame captured from the anchor position 408, anddepicting an aisle endcap. The endcap includes shelves 416-1 and 416-2bearing labels 418, as well as a pegboard region bearing labels 420(e.g. mounted on the end of pegs for supporting products). In addition,the endcap includes an aisle identifier, such as a sign 424 mounted atopthe endcap.

The data capture device, or the server 101, are configured to extractfeatures from the image data 412. In the present example, a feature setincluding three features 428-1, 428-2 and 428-3 is extracted from theimage data 412 for storage as an anchor definition (along with theanchor position 408). As illustrated in FIG. 4A, the feature 428-1includes the edges of the aisle identifier sign 424, as well as a textstring defining the aisle identifier itself. The feature 428-1 definesthe relative positions and dimensions of the edges and text string. Thefeature 428-2 includes edges, defined by their dimensions and relativepositions, of the labels 420 supported on the pegboard mentioned above.The features 482-3, meanwhile, includes the edges of the shelves 416-1and 416-2, defined by their dimensions and relative positions. Thefeature set may also store the relative positions of the features 428relative to each other (e.g. a position of the center of the feature428-1 relative to the center of the feature 428-3).

In a further example, an anchor definition can be generated by capturingone or more images as shown in FIG. 4B at the device 105. The device 105can be further configured to detect a first plane definitioncorresponding to a floor of the facility, and a second plane definition(also referred to as a shelf plane) based on one or both of the labels420 and the shelf edges 416. As will now be apparent, the floor planeand the shelf plane detected as discussed above are substantiallyorthogonal to each other. In addition, the device 105 can be configuredto capture and decode an indicium such as a barcode from at least one ofthe labels 420. The location of the label 420 from which the barcode wascaptured, relative to the floor plane and the shelf plane, can beprovided to the server, where a global location for the barcode isstored (e.g. in a planogram). Thus, a global anchor position is assignedto the anchor based on the predefined barcode location, and the anchordefinition includes the definitions of the floor and shelf planesrelative to the barcode location. A mobile device (e.g. the device 105,the apparatus 103 or the like) is therefore able to determine itscurrent global location and orientation by detecting the planes andcapturing the barcode.

A wide variety of other features may also be extracted from datacaptured along with the image data 412. As noted above, such featurescan include a list of access point RSSI and/or RTT values, a list ofbeacon identifiers, and the like.

The above process can be repeated for any desired number of anchordefinitions. In facilities including rows of shelves, such as the rows404 shown in FIG. 4A, the server 101 can be provided with at least oneanchor definition per row 404. For example, two anchor definitions maybe created for each row 404, each corresponding to one of the twoendcaps of the row 404. In other examples, smaller or greater numbers ofanchor definitions can be generated for provision to the server 101. Ingeneral, greater numbers of anchor definitions may improve the accuracyof the assistive navigational functions carried out by the server 101and the client device 105 as described below, at the cost of increaseddata storage requirements and computational load. Conversely, smallernumbers of anchor definitions may reduce computational burden on theserver 101 and/or the client device 105, while potentially reducing theaccuracy of the assistive navigational functions.

Returning to FIG. 3 , at block 310 the server 101 is configured toobtain one or more task definitions. Task definitions contain datadefining tasks to be performed within the facility, for example tocorrect or otherwise update the above-mentioned status informationdetermined by the server 101 with respect to products or other objectsin the facility. The task definitions may therefore be obtained at block310 by generating the task definitions at the server 101 itself. Inother examples, one or more task definitions may be received at theserver 101 at block 310, for example from the client device 105. Forinstance, an operator of the client device 105 may manipulate the clientdevice 105 to transmit product status information to the server 101(e.g. indicating that a product in a specified location is out of stockand requires a restocking task to be performed).

Each task definition includes a task position and task overlay data(which may also be referred to as task content). The task overlay data,as will be discussed in greater detail below, is subsequently presentedat the client device 105 to assist an operator of the client device 105in performing the corresponding task. The task overlay data maytherefore include a product identifier, a task identifier (e.g. a textstring indicating what action or sequence of actions is to be performedwith respect to the product identifier), and the like. The task positiondefines a location within the facility at which the task indicated bythe task overlay data is to be performed. In the present example, theserver 101 is configured to generate task definitions with global taskpositions, defining the location of the task according to the globalframe of reference 102. As will be seen below, however, the taskdefinitions are subsequently updated to include local task positions,defining the position of the task relative to an anchor position (e.g.the anchor position 408).

Turning to FIG. 5A, example task overlay data 500 is shown for a taskgenerated by the server 101 at block 310 responsive to detecting anincorrect price label in the facility 400 (e.g. from data captured bythe mobile automation apparatus 103). The task overlay data 500 includesan overlay template 502 having fields 504, 506 and 508. The template 502can be employed for each task definition generated by the server 101. Inother examples, however, the task overlay data 500 need not be based onsuch a shared template.

The task overlay data 500 also includes content corresponding to thefields 504, 506 and 508. In particular, the task overlay data 500includes an image 514 depicting a portion of a shelf at which the taskis to be performed. The task overlay data 500 also includes a taskdescriptor, which in the illustrated example indicates that an incorrectprice label has been detected (e.g. as highlighted in the image 514) andmust be replaced. Further, the task overlay data 500 includes a productidentifier 518, such as a name, a stock-keeping unit (SKU) identifier,or the like. The image 514, task descriptor 516 and product identifier518 are configured for rendering within the fields 504, 506 and 508respectively at the client device 105, as will be discussed below. Thetask definition can include various other overlay data in otherexamples, including instructions (e.g. text, audio, video, ormultimedia) for performing the task.

Turning to FIG. 5B, a task 520 defined by the overlay data 500 is shownwithin the facility 400. The server 101 is configured to generate a taskposition according to the frame of reference 102 at block 310, asindicated by the dashed line 524 (e.g. represented by a set ofcoordinates in the frame of reference 102). The server 101 is alsoconfigured, however, to store a local task position in the taskdefinition, which indicates the position of the task relative to ananchor position rather than to the frame of reference 102.

Returning to FIG. 3 , at block 315 the server 101 is configured toassociate each task definition obtained at block 310 with at least oneof the anchor definitions obtained at block 305. The server 101 isconfigured, based on the global position of the task definition (e.g.the position 524 of the task 520 shown in FIG. 5B), to select one of theanchor definitions. Having selected the anchor definition, the server101 is configured to determine a local task position of the taskrelative to the anchor position, based on the global positions of thetask and the selected anchor definition.

Referring again to FIG. 5B, a second anchor position 528 is shown,corresponding to an endcap of the row 404 adjacent to the endcapcorresponding to the anchor position 408. At block 315, the server 101is configured to select one of the anchor positions 408 and 528 (morespecifically, one of the anchor definitions containing the anchorpositions 408 and 528). For example, the server 101 can be configured toselect the anchor definition having the anchor position closest to theglobal position of the task 520. In other examples, the server 101 canbe configured to apply one or more additional criteria to the anchorselection at block 315. For example, when the facility 400 contains rows404 of shelves, as does the illustrated example, the server 101 can beconfigured to select only from anchors associated with the row on whichthe task 520 is located. In the illustrated example, the server 101selects the anchor definition containing the anchor position 408 forassociation with the task 520. The server 101 then determines the localtask position 532, defining the position of the task 520 relative to theanchor position 408 rather than relative to the frame of reference 102.The task definition is updated with the local task position 532 (theglobal task position may be retained in the task definition, but canalso be discarded) and an identifier of the corresponding anchordefinition. In other examples, a task may be associated with more thanone anchor definition. For example, if anchor definitions correspondingto both endcaps of the rows 404 are obtained at block 305, any taskgenerated along a given row 404 may be associated with bothcorresponding anchor definitions. That is, the task definition may beupdated with two local task positions and anchor definition identifiers.

Referring again to FIG. 3 , at block 320 the client device 105 isconfigured to update a global location of the client device 105. Theglobal location of the client device 105, in the frame of reference 102,can be updated according to any of a variety of suitable localizationmechanisms. For example, the client device 105 can be configured toprovide motion data from the motion sensor 164 as an input to a Kalmanfilter or other suitable localization algorithm. The client device 105can also be configured, in some examples, to employ proximity data suchas RSSI values and/or RTT values detected in association with wirelessaccess points, beacons or the like, to update the global location atblock 320. Updating the location of the device 105 can also be performedby detection of an anchor, if the device 105 has previously beenprovided with one or more anchor definitions.

At block 325, the client device 105 is configured to determine whetherto report the global location from block 320 to the server 101. Forexample, the client device 105 may be configured to report its globallocation to the server 101 periodically (e.g. every ten seconds) and thedetermination at block 325 can be a determination as to whether theconfigured period has elapsed since the previous location report to theserver 101. When the determination at block 325 is negative, the clientdevice 105 continues updating the global location at block 320.

When the determination at block 325 is affirmative, the client device105 sends its current global location (i.e. in the frame of reference102) to the server 101 at block 330. The client device 105 typicallycontinues to update the global location and periodically report theglobal location in parallel with the remainder of the method 300.

At block 335, the server 101 is configured to receive the globallocation of the client device 105. At block 340, the server 101 isconfigured to determine whether to allocate one or more tasks to theclient device 105. In the present example the determination at block 340is based on the global location of the client device 105. Specifically,the server 101 is configured to allocate a task to the client device 105based on proximity between the current (i.e. most recently reported)location of the client device 105 and the global position of the task.In examples in which the global task position is not retained followingthe performance of block 315, the server 101 is configured to allocatetasks to client devices 105 based on proximity between client device 105location and anchor position (both in the frame of reference 102).

In other examples, the determination at block 340 can be based on otherfactors in addition to the location of the client device 105, and incertain examples the determination at block 340 is independent of thelocation of the client device 105. For example, the server 101 can beconfigured to allocate tasks to client devices 105 based on whether ornot each client device 105 has been allocated a task, regardless of thelocation of the client device 105.

Other examples of criteria assessed by the server 101 at block 340includes capabilities of the client device 105 or an associated operator(e.g. identified via login credentials provided at the input device156). For example, the server 101 can maintain a list of client devices105 and associated input and output capabilities, such as an indicationof whether a client device 105 includes a label printer suitable forcompleting a price label correction task. Thus, the task descriptor andthe client device capabilities, in addition to or instead of clientdevice location, can be assessed by the server 101 at block 340.

When the determination at block 340 is negative, the server 101 isconfigured to await further location reports from the client device 105,and may also obtain additional task definitions (e.g. in response tofurther data collection activities by the mobile automation apparatus103). When the determination at block 340 is affirmative, however, atblock 345 the server 101 is configured to select at least one of thetask definitions obtained at block 310 according to any of the criterianoted above, and to send both the task definition and the associatedanchor definition (i.e. the anchor definition associated with the taskdefinition at block 315) to the client device 105. Thus, at block 345the server 101 is configured to transmit at least one task definition,containing the task overlay data and local task position, as well as theanchor definition according to which the local task position is defined,to the client device 105.

At block 350, the client device 105 is configured to receive and storethe task and anchor definitions in the memory 152. The client device 105is also configured to initiate an assistive navigational process atblock 350. In the present example, the client device 105 is configuredto capture a sequence of images using the camera 158 responsive toreceiving the task and anchor definitions. The sequence of images areemployed by the client device 105 to detect the feature setcorresponding to the anchor definition received at block 350.

At block 355, the client device 105 is configured to present an anchorguide prompt, e.g. on the display 160 (although guide prompts can alsobe presented via other output devices, such as audible prompts via aspeaker). The guide prompt presented at block 355 indicates thedirection and optionally the distance from the current global positionof the client device 105 to the global position of the anchor definitionreceived at block 350. Referring briefly to FIG. 5B, a current position536-1 of the client device 105 is illustrated. Turning to FIG. 6 , ananchor guide prompt 600 is shown as presented on the display 160 of theclient device 105. In particular the client device 105 presents not onlythe anchor guide prompt 600, but also the sequence of images whosecapture was initiated at block 350. Thus, the display 160 also presentsan image 604 from the sequence of images, depicting the current field ofview of the camera 158. As will now be apparent, the anchor guide prompt600 indicates the direction of travel required to arrive at the anchorposition 408 (which is adjacent to the endcap of the row 404).

At block 360, the client device 105 is configured to determine whetherthe feature set of the anchor definition received at block 350 has beendetected in one or more of the sequence of images captured using thecamera 158. That is, the client device 105 is configured, for each ofthe sequence of images, to identify candidate features such as planes,lines, points and the like, and to determine whether the candidatefeatures identified match any of the features in the feature set of theanchor definition received at block 350.

In the present example performance of the method 300, it is assumed thatthe features 428-1, 428-2 and 428-3 as shown in FIG. 4B are not detectedin the image 604 presented in FIG. 6 . The client device 105 thereforereturns to block 355, and continues presenting the anchor guide prompt600, updating the orientation of the anchor guide prompt according tothe global position of the client device 105 relative to the globalanchor position 408. Turning to FIG. 7A, an updated position 536 a ofthe client device 105 is shown adjacent to the endcap of the row 404-3.FIG. 7B illustrates an image 700 in the sequence of images whose capturewas initiated at block 350. As will be apparent from FIG. 7B, thefeatures 428 of the anchor definition are detectable in the image 700.The determination at block 360 is therefore affirmative. Further,distortions between the features 428 as represented in the image 700 andthe features 428 as defined in the anchor definition shown in FIG. 4Benable the client device 105 to determine the position of the clientdevice 105 relative the anchor position 408.

In other words, detection of the anchor at block 360 causes the clientdevice 105 to initiate a local navigation mode at block 365, in whichthe client device 105 is configured to determine and update a localdevice position relative to the anchor position 408. The device maycontinue to update the global location mentioned above in connectionwith block 320, but the remaining blocks of the method 300 are performedby the client device based on the local device position, which may besubject to reduced errors (e.g. errors incurred due to drift in themotion sensor 164) in comparison to the global location of the clientdevice 105. The local navigational mode includes the use of not only themotion sensor 164 and communications interface 162 (for detectingwireless access point signatures), but also of the camera 158 and inparticular the sequence of images whose capture was initiated at block350. Specifically, the client device 105 can be configured to detecttransient features in a subset of the images (e.g. planes, lines, pointsand the like) and to track changes in positions of such transientfeatures within the images so long as the transient features remainvisible. The client device 105 is then configured, based on detectedchanges in position of the transient features between images in thesequence, to update the local device position.

FIG. 8A illustrates a further overhead view of the facility 400,following travel of the client device 105 to a further position 536 b.The client device 105 is configured to maintain an updated local deviceposition 800 relative to the anchor position 408 (e.g. employing theanchor position 408 as the origin of a local frame of reference). Atblock 370 the client device 105 is configured to present a task guideprompt, indicating a direction of travel and optionally a distance tothe task position, determined according to the task position specifiedin the task definition and the local device position 800. FIG. 8Billustrates a task guide prompt 804 presented on the display 160 alongwith an image 808 of the above-mentioned sequence. Also shown in FIG. 8Bare examples of the transient features noted above, employed for localnavigation. In particular, a shelf edge 812 and a product 816 may beidentified by the client device 105 in the image 808 as well as asubsequent image. Based on changes in the positions of the shelf edge812 and the product 816 between images, the client device 105 candetermine an updated local position.

Referring again to FIG. 3 , at block 375 the client device 105 isconfigured to determine whether the task position is within a field ofview of the client device 105. The determination at block 375 is madebased on the task position (which is a local position, defined relativeto the anchor position 408) and the local device position, as well as ona field of view definition stored in the memory 152. An example field ofview 820 is shown in FIG. 8A, and may correspond to the field of view ofthe camera 158. As is evident from FIG. 8A, the task position 520 is notwithin the field of view 820, and the determination at block 375 istherefore negative. Following a negative determination at block 375, theclient device 105 is configured to return to block 370 to update thetask guide prompt based on the current local device position. Block 375is then repeated.

When the determination at block 375 is affirmative, the performance ofthe method 300 proceeds to block 380. Turning to FIG. 9A, a furtheroverhead view of the facility 400 is shown, in which the client device105 has advanced further into the aisle containing the task 520, to aposition 536 c, tracked at the client device 105 as a local deviceposition 900. The client device 105 has also been reoriented towards therow 404-3 of shelves, and the determination at block 375 is affirmative(the task position 520 falls within the field of view 820). At block380, therefore, the client device 105 is configured to present the taskoverlay data on the display 160 along with the above-mentioned sequenceof images. In other words, the task overlay data is presented on thedisplay as an augmented reality overlay (i.e. a virtual object) on thestream of images captured by the camera 158.

FIG. 9B illustrates a performance of block 380, with the client device105 at the position 536 c shown in FIG. 8A. In particular, an image 904from the sequence initiated at block 350 is presented on the display160, along with a virtual object overlay 908 containing the task overlaydata 500 discussed earlier in connection with FIG. 5A. The performanceof the method 300 thus enables the client device 105 to aid an operatorof the client device 105 in locating a task position within thefacility, and in performing the corresponding task.

Variations to the above systems and methods are contemplated. Forexample, in some embodiments the local device position mentioned abovein connection with block 365 can be presented, e.g. on the display 160of the client device 105, even in the absence of a task definition. Forexample, the device 160 can be configured, following detection of ananchor such as the aisle endcap shown in FIG. 7B, to present a map ofthe facility, or a portion thereof (e.g. a map of the correspondingaisle). Overlaid on the map, the device 105 can be configured to presentan indication of the location of the device 105, as determined at block365.

As mentioned previously, task definitions obtained by the server 101 atblock 310 can be received from the client device 105. In particular, insome embodiments the client device 105 is configured to update a globallocation as at block 320, and to receive anchor definitions as discussedabove in connection with block 350. However, the client device 105 neednot receive task definitions. Instead, having detected an anchor atblock 360, such as an endcap of an aisle (e.g. as shown in FIG. 7B), theclient device 105 is configured to initiate local navigation and tocapture one or more barcodes or other indicia.

The indicia captured by the client device 105 correspond to labels onthe shelves 110 at which one or more tasks are required (e.g. to restocka product, correct a price on the label, or the like). The client device105 is configured to determine a location of each scanned indicium basedon the local navigation and the global location of the client device 105itself, as well as on the location of the indicium relative to theclient device 105. For example, the relative location of the indiciumcan be determined from an image of the indicium based on calibrationparameters of the camera 158 along with dimensions of the indiciumwithin the image.

Having located the scanned indicium in the facility (i.e. relative tothe frame of reference 102), the client device 105 can be configured toreceive input data defining task overlay data, such as an indication ofthe type of task to be performed (e.g. restock). The location of theindicium corresponds to the above-mentioned task position, and istransmitted along with the task overlay data to the server 101 forstorage as a task definition.

In further embodiments, as noted earlier, the server 101 can beconfigured to perform certain blocks shown in FIG. 3 as being performedby the client device 105, and/or the client device 105 can be configuredto perform certain blocks shown in FIG. 3 as being performed by theserver 101. For example, in another embodiment the server 101 can beconfigured to determine a location of the client device 105 at block320. Blocks 325, 330 and 335 can therefore be omitted. The server 101can also be configured to receive image data captured by the clientdevice 105 and detect anchors therein. In other words, rather thansending task and anchor definitions to the client device 105 at block345, the server 101 is configured to select the task and anchordefinitions, and the client device 105 is configured to capture and sendimages to the server 101 at block 350. The server 101, in turn, isconfigured to generate and send an anchor guide prompt to the clientdevice 105 for presentation at block 355, and to perform thedetermination at block 360. The server 101 can be further configured toperform the processing associated with local navigation at block 365,and to generate and send the task guide prompt to the client device 105for presentation at block 370. Still further, the server 101 can beconfigured to perform the determination at block 375 (based on capturedimages received from the client device 105) and to generate and send thetask overlay for presentation by the client device 105 at block 380.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has”,“having,” “includes”, “including,” “contains”, “containing” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises, has,includes, contains a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus. An element proceeded by“comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . .a” does not, without more constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises, has, includes, contains the element. The terms“a” and “an” are defined as one or more unless explicitly statedotherwise herein. The terms “substantially”, “essentially”,“approximately”, “about” or any other version thereof, are defined asbeing close to as understood by one of ordinary skill in the art, and inone non-limiting embodiment the term is defined to be within 10%, inanother embodiment within 5%, in another embodiment within 1% and inanother embodiment within 0.5%. The term “coupled” as used herein isdefined as connected, although not necessarily directly and notnecessarily mechanically. A device or structure that is “configured” ina certain way is configured in at least that way, but may also beconfigured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors andfield programmable gate arrays (FPGAs) and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod and/or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the two approaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

The invention claimed is:
 1. A method of navigational assistance at amobile computing device for deployment in a facility having a globalframe of reference, the method comprising: in a global navigation mode,determining a global device position in the global frame of reference;receiving an anchor definition containing (i) an anchor position in theglobal frame of reference, and (ii) a feature set corresponding tophysical characteristics of the facility at the anchor position;receiving a task definition containing (i) a task position definedrelative to the anchor position, and (ii) task overlay data; capturing,using an image capture module, a sequence of images; responsive todetecting the feature set of the anchor definition in the sequence ofimages, switching from the global navigation mode to a local navigationmode by determining a local device position of the mobile computingdevice relative to the anchor position; based on the local deviceposition and the task position, determining whether the task position iswithin a field of view of the mobile computing device; responsive todetermining that the task position is within the field of view,presenting the sequence of images overlaid with the task overlay data ona display.
 2. The method of claim 1, further comprising: prior toreceiving the anchor definition and the task definition, determining theglobal device position of the mobile computing device and sending theglobal device position to a server; and receiving the anchor definitionand the task definition responsive to sending the global deviceposition.
 3. The method of claim 1, wherein determining the local deviceposition comprises: identifying transient features in the sequence ofimages and tracking the local device position based on movement of thetransient features between images in the sequence.
 4. The method ofclaim 1, wherein the feature set corresponds to (i) a visual appearanceof physical structures in the facility and (ii) a proximity indicatorcorresponding to the proximity of the anchor position to a wirelesstransmitter; and wherein the method further comprises: capturingsimultaneously with the sequence of images, using at least one of theimage capture module and a communications interface, proximitysignatures; wherein detecting the feature set includes (i) detecting thevisual appearance in the sequence of images, and (ii) detecting theproximity indicator in the proximity signatures.
 5. The method of claim4, wherein the proximity indicator includes at least one of: a receivedsignal strength indicator (RSSI) corresponding to a wireless accesspoint; a round trip time (RTT) corresponding to the wireless accesspoint; an identifier of a wireless beacon; and an identifier of a visuallight communication (VLC) emitter.
 6. The method of claim 1, whereinpresenting the sequence of images and the overlay data includesselecting a portion of the image corresponding to the task location, andpresenting the overlay data on the selected portion.
 7. The method ofclaim 1, further comprising: responsive to determining that the taskposition is not within the field of view, presenting a task guide prompton the display indicating the task position relative to the local deviceposition.
 8. The method of claim 1, wherein the overlay data includes atleast one of a task descriptor and an object identifier.
 9. A mobilecomputing device for navigational assistance in a facility having aglobal frame of reference, the mobile computing device comprising: amemory storing: an anchor definition containing (i) an anchor positionin the global frame of reference, and (ii) a feature set correspondingto physical characteristics of the facility at the anchor position; anda task definition containing (i) a task position defined relative to theanchor position, and (ii) task overlay data; a display; an image capturemodule configured to capture a sequence of images; a processor connectedto the memory, the display and the image capture module, the processorconfigured to: in a global navigation mode, determine a global deviceposition in the global frame of reference; responsive to detecting thefeature set of the anchor definition in the sequence of images, switchfrom the global navigation mode to a local navigation mode bydetermining a local device position of the mobile computing devicerelative to the anchor position; based on the local device position andthe task position, determine whether the task position is within a fieldof view of the mobile computing device; and responsive to determiningthat the task position is within the field of view, control the displayto present the sequence of images overlaid with the task overlay data ona display.
 10. The mobile computing device of claim 9, furthercomprising: a communications interface; and a motion sensor configuredto generate motion data; wherein the processor is further configured,prior to receiving the anchor definition and the task definition forstorage in the memory, to determine the global device position of themobile computing device based on the motion data, the processor furtherconfigured to send the global device position to a server via thecommunications interface.
 11. The mobile computing device of claim 9,wherein the processor is further configured to determine the localdevice position by identifying transient features in the sequence ofimages and track the local device position based on movement of thetransient features between images in the sequence.
 12. The mobilecomputing device of claim 9, further comprising a communicationsinterface; wherein the feature set corresponds to (i) a visualappearance of physical structures in the facility and (ii) a proximityindicator corresponding to the proximity of the anchor position to awireless transmitter; wherein the processor is further configured tocontrol at least one of the image capture module and the communicationinterface to capture, simultaneously with the sequence of images,proximity signatures; and wherein the processor is further configured,to detect the feature set, to (i) detect the visual appearance in thesequence of images, and (ii) detect the proximity indicator in theproximity signatures.
 13. The mobile computing device of claim 12,wherein the proximity indicator includes at least one of: a receivedsignal strength indicator (RSSI) corresponding to a wireless accesspoint; a round trip time (RTT) corresponding to the wireless accesspoint; an identifier of a wireless beacon; and an identifier of a visuallight communication (VLC) emitter.
 14. The mobile computing device ofclaim 9, wherein the processor is further configured to present thesequence of images and the overlay data by selecting a portion of theimage corresponding to the task location; the processor furtherconfigured to present the overlay data on the selected portion.
 15. Themobile computing device of claim 9, wherein the processor is furtherconfigured, responsive to determining that the task position is notwithin the field of view, to present a task guide prompt on the displayindicating the task position relative to the local device position. 16.The mobile computing device of claim 9, wherein the overlay dataincludes at least one of a task descriptor and an object identifier.